DESCRIPTION (Directly incorporated from the application) The Washington Hospital Center/Medlantic Research Institute and the Howard University Medical School will collaborate in an effort to identify and enroll African Americans at risk for the development of IGT and NIDDM into a primary prevention trial. We will concentrate on recruitment of African Americans because of the disproportionate effect diabetes has on this community and the fact that Washington DC, with 70 percent African Americans, is estimated to have 52,000 citizens with diabetes, with half undiagnosed. The unique aspects of NIDDM in the African American population together with their disproportionate prevalence demand inclusion of African Americans as a major component of any primary prevention trial for NIDDM. Impaired glucose tolerance is the optimal time when interventions aimed at reversing the insulin resistance may prevent the progression of carbohydrate intolerance to NIDDM. We propose an efficient recruitment strategy based on the documented availability of groups enriched in the proportion of individuals with abnormal glucose tolerance. These include clinic patients seen at the Washington Hospital Center (WHC) and Howard University Hospital (HUH) who are obese and have relatives with NIDDM, patients with premature cardiovascular disease, and patients with a history of gestational diabetes. We propose a two by two factorial design to investigate aggressive lifestyle modification (diet and exercise), and pharmacologic intervention with metformin. Culturally appropriate interventions and follow-up techniques based on community support and input are presented designed to enhance retention and compliance. Primary endpoint determinations will be progression form IGT to NIDDM. Improvement of carbohydrate tolerance in newly diagnosed NIDDM will also be examined. Secondary end points include metabolic parameters related to insulin resistance, insulin secretion, lipoprotein changes and cardiovascular endpoints such as hypertension. Our center is experienced in the conduct of clinical trials and is committed to working with the Steering Committed in the design and conduct of the Trial.